French patent application No. 2,288,318 describes an optical fibre cable of the above type in which the central filament is made of a plastics material and is in the form of a spoked wheel with a core formed by steel wires and grooves separated by thin partitions. However, its thin plastics partitions make it somewhat fragile, whereas it must be suitable for winding onto and off cable drums and for handling during laying. Preferred embodiments of the present invention provide a very strong underwater optical fibre cable which can be readily handled without taking particular precautions during laying.